Natural and experimental high‑pressure, shock‑produced terrestrial and extraterrestrial materials

AbstractHypervelocity impacts are among the fundamental phenomena occurring during the evolution of the solar system and are characterized by instantaneous ultrahigh pressure and temperature. Varied physicochemical changes have occurred in the building blocks of celestial bodies under such extreme conditions. The constituent material has transformed into a denser form, a high-pressure polymorph. The high-pressure polymorph is also thought to be the constituent of the deep Earth's interior. Hence, experiments using a high-pressure and temperature generating apparatus have been conducted to clarify its crystal structure, pressure–temperature stability range, and transformation mechanisms. A natural high-pressure polymorph (mineral) is found from terrestrial and extraterrestrial rocks that experienced a hypervelocity impact. Mineralogists and planetary scientists have investigated high-pressure minerals in meteorites and rocks near terrestrial craters over a half-century. Here, we report brief reviews about the experiments producing high-pressure polymorphs and then summarize the research histories of high-pressure minerals occurring in shocked meteorites and rocks near terrestrial craters. Finally, some implications of high-pressure minerals found in impact-induced shocked rocks are also mentioned. Graphic abstrac

The systematic investigations of high-pressure polymorphs in shocked L type ordinary chondrites

第6回極域科学シンポジウム[OA] 南極隕石11月16日（月）　国立国語研究所 2階 講

Petrography of Yamato 984028 lherzolitic shergottite and its melt vein: Implications for its shock metamorphism and origin of the vein

AbstractYamato 984028 (Y984028) is a newly identified lherzolitic shergottite, recovered from the Yamato Mountains, Antarctica, in 1999. As part of a consortium study, we conducted petrographic observations of Y984028 and its melt vein in order to investigate its shock metamorphism. The rock displays the typical non-poikilitic texture of lherzolitic shergottite, characterized by a framework of olivine, minor pyroxene (pigeonite and augite), and interstitial maskelynite. Shock metamorphic features include irregular fractures in olivine and pyroxene, shock-induced twin-lamellae in pyroxene, and the complete conversion of plagioclase to maskelynite, features consistent with those found in other lherzolitic shergottites. The melt vein is composed of coarse mineral fragments (mainly olivine) entrained in a matrix of fine-grained euhedral olivine (with several modes of compositional zoning) and interstitial glassy material. Some coarse olivine fragments consist of an assemblage of fine-grained euhedral to subhedral olivine crystals, suggesting shock-induced fragmentation, recrystallization, and/or a process of sintering. The implication is that the fine-grained olivine crystals in the matrix of the melt vein represent complicated crystallization environments and histories

Investigation of organic matter in the Allende meteorite using scanning transmission X-ray microscope at photon factory

第6回極域科学シンポジウム[OA] 南極隕石11月16日（月）　国立極地研究所１階交流アトリウ

New coronary aneurysm formation and malapposition after zotarolimus-eluting stent implantation in Kawasaki disease

AbstractCoronary artery involvement is the most important complication of Kawasaki disease. Coronary artery bypass surgery has been performed for ischemic heart disease caused by Kawasaki disease, however, long-term coronary graft patency is not satisfactory. Therefore, percutaneous coronary intervention (PCI) has its role in Kawasaki disease-related coronary artery disease. The incidence of new aneurysm is lower following stent implantation than balloon dilatation alone, even if a higher balloon pressure is applied. However, there are few reports about the efficacy of drug-eluting stent implantation for Kawasaki disease with coronary artery disease. Here, we describe a case of new coronary aneurysm formation and malapposition after zotarolimus-eluting stent implantation in Kawasaki disease.<Learning objective: New aneurysm formation after balloon angioplasty for coronary artery lesions in Kawasaki disease is a relatively well-known phenomenon, however there have been no reports about the influence of drug-eluting stents for coronary artery disease with Kawasaki disease. This report is useful when we consider strategies of revascularization for coronary artery disease with Kawasaki disease.

The investigation of back-transformation mechanisms of ringwoodite and majorite in the Yamato 75267 H6

The Tenth Symposium on Polar Science/Special session: [OA] Antarctic meteorites, Thur. 5 Dec. / 3F Multipurpose conference room, National Institute of Polar Researc

Discovery of natural MgSiO3 tetragonal garnet in a shocked chondritic meteorite

MgSiO3 tetragonal garnet, which is the last of the missing phases of experimentally predicted high-pressure polymorphs of pyroxene, has been discovered in a shocked meteorite. The garnet is formed from low-Ca pyroxene in the host rock through a solid-state transformation at 17 to 20 GPa and 1900° to 2000°C. On the basis of the degree of cation ordering in its crystal structure, which can be deduced from electron diffraction intensities, the cooling rate of the shock-induced melt veins from ~2000°C was estimated to be higher than 103°C/s. This cooling rate sets the upper bound for the shock-temperature increase in the bulk meteorite at ~900°C